looks like u covered everythingBy the time this one comes out, it will be 12 years after Indy 4. If they use that continuity, Indy 5 will take place in 1970 (though it could also be bumped back a couple years to 1968). Shia can pop in for a quick cameo, show off Henry Jones IV or whatever, and leave for the rest of the film.
Raiders was set in 1936, focused on pre-WWII adventure of Biblical proportions fighting Nazis
Temple of Doom- 1935- Jungle adventure & magic
Last Crusade- 1938- Nazis and biblical adventures, Father-son bonding time
Crystal Skull- 1957, ends in 1958- Communists, Jungle, Father-son bonding time, Aliens (am I missing anything? There was a lot packed into that one)
Indy 5- late 1960s, early 1970s- could be communists, maybe set in Vietnam, the return of Sallah (please, Spielberg, he won't do it if it's only a cameo)